Spinal surgeons often treat spinal disorders with spinal fusion augmented with elongated spinal rods connected to the spine with pedicle screws. Such “rod assemblies” generally comprise one or two spinal rods and a plurality of screws inserted through the pedicles and into their respective vertebral bodies. The screws are provided with connectors, for coupling the spinal rods to the screws. The spinal rods extend along the longitudinal axis of the spine, coupling to the plurality of screws via their connectors. The aligning influence of the rods forces the patient's spine to conform to a more appropriate shape.
Those bone screw connectors often employ tabs or towers to facilitate the assembly. Once the screws and rods are fixed in place, these tabs or towers are removed from the connector. Various means to remove the tabs have been used including releasable pins and frangible tear or fracture seams. The tabs or towers often called extension legs vary in length from short, an inch or less, to very long, four or more inches. The removal of these extension legs needs to be simple and reliable. Most preferably, the removal needs to be consistent. The attachment must be secure so as not to prematurely fail, but not so strong as to require large forces or multiple flexing to release the legs. Some prior art bone screws have resorted to separate tools to initiate a breakage of a connection due in part to the excessive forces required, as taught in U.S. Pat. No. 7,927,360.
It is an object of the present invention to provide an easier to use, more reliable breakaway feature.